1. Field of the Invention
This invention relates to a reliable method of carrying out at a high speed treatment for removing chips that cause and a treatment for eliminating inner wall roughening that occur during the boring of small holes in a substrate.
2. Description of the Prior Art
In prior methods, when a boring operation of a double face copper-lined epoxy resin substrate incorporating a glass fiber as a substrate material of an electronic device is carried out, holes having a diameter of greater than 0.3 mm are bored, and the resulting chips are ordinarily removed by a method as ultrasonic washing. Recently, however, wiring is made in a miniature pattern having a high density and a multi-layered structure, and along therewith, diameters of through-holes become as small as about 0.25 mm to about 0.1 mm. Consequently, clogging due to chips, coarsening of inner walls and fins occur frequently due to problems such as wear and breakage of a cutting edge of a drill, and the ultrasonic washing method can no longer remove the chips, inner wall coarsening and the fins.